Frequency divider



Patentecl Feb. 22, 1949 UNITED STATES PATEN T F F ICE (FREQUENCY DIVIDER Charles J. Hirsch, Bouglastom-N. Y assignor, by

irresne assignments, to Hazeltine Research, lnc.,

Chicago, Hl.,-: a corporation. Hlinois Applicationiiugust 16, 1944.;SeriaYNo. 549,743

'5 Claims. (01. 250- 27) The'pr'esent invention relates to frequency dividers and, particularly, to such dividers wherein a relatively low-periodicity'recurrent pulse signal is derived from a higher-periodicity recurrent-pulse signal.

There are many applications where it is desirable to derivaby a process of frequency division, a relatively low-periodicity recurrent-pulse signal from an input recurrent-pulse signal of relati-vely high periodicity. Multivibrators or relaxationoscillators'have heretofore been conventionally usedfor this purpose, the .multivibrator generating thelow-periodicity signal .and having an eperaticn synchronized by the high-periodicity inputsignal. There is the limitation and disadvantage with frequency dividers of thistype that the-periodicity of the derived signal. must be inteeral with that of the input signal. There is-the additional disadvantage for certain-applications that the waveform of the derived signal does not necessarily correspond with that of the input signal, since the former is determined solely by the values-of the circuit components of the multivibrator, and may require the "use of additional wave shapingcircuitsto conform the Wave shapes of the two signals.

A frequency divider which avoids the last-mentioned disadvantage is disclosed in the copending United States patent application of Robert B. J. Brunn, Serial No. 524,0'7-8, filed February 26, 1944, entitled Signal-translating system, now aban cloned, and-assigned to'the sameiassignee as the present application. In this arrangement, the input recurrent-pulse signal is translated through a repeater device to a synchronizing circuit of a univibrator. A pulse of the input signal initiates a cycle of operation of the univibrator which thereupon deenergizes the repeater device during the remaining portion of the cycle'of operation of the univibrator, thus preventing the application to the latter of any additional pulses of the input signal. After the univibrator hascompleted its cycle of operation, however, the repeater device becomes again energized to translate the heft pulse of the input signal to the univibrator to initiate another cycle-of its operation. The output recurrent-pulse signal of this system has a periodicity which is integral'with that of the input signal.

It is an object of the present invention, therefore, to provide a newan'd improved frequency divider which avoids one or more of the disadvantages "and limitations of prior devicesof the type described. a

t is an additional objector the invention to 2 provide a new and improved frequency divider which enables the attainment of a nonintegra'l frequency division from 'a higher-periodicity 'recurrent-pulse signal to a.lower periodicityrecurrent pulse signal.

"It is a-further object of the "invention to provide a frequency divider of simplified and improved circuit arrangement wherein a recurrentpulse signal of relatively .low periodicity may "be derived from a recurrent-pulse signal of higher periodicity, the former having an average-periodicity whichisnonintegrzil With'that of the lastmentioned signal but a predetermined constant time or synchronous relationship therewith.

In accordance with the invention, a frequency divider comprises a first input circuit. adapted to have applied thereto a ,higheperi-odicity recurrent-pulse signal, asecondinput circuit adapted to have appliedtheretoa periodic control vsi nal having .a ,-.periodicity substantially lower than thatof the first-mentioned signal andnon-integral with respect thereto, and repeatermeans for combining these signals and responsive to the combined amplitudes thereof for repeating during each periodwofuthe control signalonlya portion of the vcombinedsignals including only a limited numberof pulses of. the first-mentioned signal. The divider includes pulse-responsive means responsive to at least one selected -;,pulse of the repeated pulses occurring during each period of the control signal for initiating .a ,pulse of a recurrent-pulse signal, andforthereafter renderingxthe pulse-responsive, means unresponsive to. any pulse repeated during the remaining portion of the period of translationof the combined 'signalsfollowing theone selected -pulse. The :frequency divider also includes a. signaltran'slating channel coupled/to ,thewfirstinput circuit and responsive to "the last-mentioned, recurrent-pulse signal for translating duringweach pulse thereof the"first-mentioned si nal to derive a recurrentepulse signal having a. predetermined time relationship with'the"first-mentioned signal but'an average periodicity equal to thatof "the control signal.

"For a better understanding, of the present .invention, together'with other and furtherobjects thereof, reference is had to thefollowing description taken in connection with the accompanying drawing; and its scope Willbe pointedoutin the appended claims.

Referring now to the .drawing, .Fig. lnisa circuit diagram, partly schematic, of a complete radiant energy jsystem' illustrated .as of the, type for locating and identifying a radiated-signal refiector, such as an aircraft or naval vessel, which embodies the frequency divider of the present invention in a particular form; and Fig. 2 graphically represents potential relationships occurring at selected points in the frequency divider of the Fig. 1 system and is used as an aid in explaining the operation thereof.

Referring now more particularly to Fig. 1, there is represented a circuit diagram, partly schematic, of a complete radiant-energy system of the type for locating and identifying a radiated-signal reflector, such as an aircraft or a naval vessel, which embodies the frequency divider of the present invention in aparticular form. The system includes a radiated-signal reflector-locating system In coupled to an antenna H, usually having a sharply directive characteristic. The system H) essentially comprises a pluse-modulation system and includes a plusesignal generator and transmitter for generatin a pulse-modulated wave signal, which is applied to the antenna II for radiation thereby, and a receiver having an input circuit coupled to the antenna H and having an output circuit coupled to vertical-deflecting electrodes of a cathoderay tube l2, as indicated by V. The system applies the pulses of the pulse signal generated thereby as synchronizing pulses to a. horizontalscanning generator 9, which in turn supplies horizontal-scanning potentials to horizontal-defleeting electrodes of cathode-ray tube [2, as indicated by H, to provide horizontal scanning of the cathode-ray beam thereof, each horizontalscanning line T being initiated by a modulation pulse applied to the transmitter of the system H).

The pulse-signal generator of unit [0 is also coupled through a frequency divider l3, presently to be described in greater detail, to a modulation circuit of an identifying system 14. The latter includes a pulse-modulation transmitter, having the modulation input circuit mentioned and having an output circut coupled through a singlepole double-throw switch l5 selectively to either of two antenna systems [6 or IT. The identifying system M also includes a receiver having an input circuit coupled through the same switch selectively to either of the antenna systems Iii-or I1 and an output circuit coupled to the vertical-deflecting electrodes of the cathode-ray tube [2, as indicated at V. The antenna systems l6 and I! have sharply directive characteristics which partially, overlap one another. To effect periodic and alternate selection of the antenna systems l6, H, the movable contact of the switch I5 is operated by an electromagnet l8 which is energized from an alternating current source [9 having a frequency, for example, of 60 cycles per second. The recurrent-pulse output signal of unit I3 is also applied to a univibrator which is effective upon application of a pulse thereto to generate a pulse initiating with the synchonizing-pulse input of unit and having a duration substantially as long as the saw-tooth duration of the scanning potential provided by unit 9. The pulse output of unit 20 is applied to unit 10 to cause the receiver of unit ill to be inoperative during the period of each applied pulse. Alternate pulses generated by unit 20 are applied to unit 9 and added therein to the developed sawtooth scanning potential for a purpose which will be explained more fully hereinafter.

It will be understood that the various units just described may, with the exception of the frequency divider l3, be of a conventional construction and operation, the details of which are well known in the art, rendering a detailed description thereof unnecessary. Considering briefly the operation of the system as a whole, and neglecting for the moment the operation of the frequency divider l3 presently to be described, pulse-modulated wave signals are generated by the transmitter of the system 10 and are radiated by the antenna H to a distant radiated-signal reflector, for example an aircraft or naval vessel. Radiated-signal energy is reflected by the latter and a portion of the reflected energy is received by the antenna H and applied to the receiver of the locating system Ill. The receiver suitably amplifies the received wave signal, derives and amplifies the modulation components thereof, and applies them to the vertical-deflecting electrodes of the cathode-ray tube i2.

The horizontal deflection of the cathode-ray beam of tube I2 is initiated by the modulation pulses applied to the transmitter of system [0 and varies linearly with time. The modulation components applied by the receiver of system ii to the vertical-deflecting electrodes of tube l2 produce a vertical deflection P on the horizontal trace T. The distance of the vertical deflection P from an end of the trace T is indicative of the distance of the radiated-signal reflector from the locating system.

The pulse-modulation signal applied to the transmitter of system 10 is also applied to the frequency divider l3. This modulation signal is of the recurrent-pulse type having a relatively high periodicity and there is derived therefrom by the frequency divider l3 and applied toa modulation circuit of the identifying system H a lower-periodicity recurrent-pulse signal which is used to pulse-modulate a wave signal generated by the transmitter of unit [4. This pulsemodulated wave signal, which may be considered an interrogating signal, is radiated from one of the antenna systems I6 or H, depending upon which of the antenna systems is selected at a given moment by the switch Hi. The radiated wave signal is propagated to the distant radiatedsignal reflector. If the latter is equipped with suitable transpondor equipment for receiving the interrogating signal and for replying thereto, the reply wave signal is received by the same antenna system which radiated the wave-signal energy and is applied to the receiver of system I l. The received wave signal is suitably amplified by the receiver and the modulation components thereof are derived, amplified, and applied to the verticaldefiecting electrodes of tube l2, preferably with opposite polarity to the modulation components applied to the vertical-deflecting electrodes of tube 12 from the locating system Ill. The resulting vertical deflection P produced on the horizontal trace T is directly below the deflection P and produces an indication by which to identify the distant radiated-signal reflector.

The periodicity of the recurrent-pulse signal which modulates the wave signal of system In is much higher than that of the recurrent-pulse signal applied from unit I3 to the identifying system l4. Illustrative values in this regard are 800 and pulses per second for these signals. This permits what may be called an interlacing of the displays produced on the fluorescent screen of tube l2 by the locating system l0 and the identifying system H. To this end, the recurrentpulse signal developed in the output circuit of the unit I3 is applied to univibrator 20- to develop in the output circuit of the latter a recurrent-pulse signal having one pulse for each pulse of the Signal applied'to unit 20 and apulse duration substantially equal to the saw-tooth duration of unit 9; The periodic-pulse output signal of the multivibrator 20 isused to perform two functions. The first of these is to reduce to zero the output of the receiver of system It] upon the occurrence of each pulse of the signal applied to univibrator 20, the receiver remaining deenergized for an interval corresponding to a complete horizontal trace of tube l2. The second function of the periodicpulse output signal of univibrator'20 is to effect a horizontal displacement of'the trace of tube H by a small constant value upon the occurrence of alternate pulses of this signal. As will presently be explained in greater detail, there are two pulses of the periodic-pulse signal derived by unit it for each complete cycle of the alternatingpotential of source 19. The operation of the switch 15 under thecontrol of the electromagnet I8 is such that theantenna systems I6, I! are alternately con nectedto unit It during alternate half cycles of the potential of source IS, the connection of either antennato unit l4 being maintained for a period sufficiently long for an interrogating pulse to be radiated to the remote transponder equipment andfor the reply pulse to be received by the same antenna system.

As a consequence, the periodic horizontal displacement of the trace of tube l2 previously described has the effect ofproducing a small horizontal displacement between the vertical deflection P" produced by the operation of one of the antenna systems 5 or H and the vertical deflection P" produced by operation of the other an tenna system. The antenna systems it and I! are rotatably supported about a vertical axis and, by virtue of their overlapping directional radiation characteristics, may be rotated until the vertical deflections P and P" have equal amplitude, at Which time it is known that the position of the transpondor equipment is normal to the axis of alignment of the antenna systems it and Il. This aids in correlating and identifying the response of an answering transpondor equipment with one or more indications P produced on the screen of tube I2 by the operation of the locating system H).

In the operation of the locating system to, it is essential that each horizontal trace T of the tubel2 be initiated in timed relation to the moment of radiation of individual wave-signal pulses by the antenna H. It 'is further essential for the coordinated operation of the locating system I 0 and the identifying system M that the moment of radiation of individual wave-signal pulses by either of the antennas It or ll, depending upon. which of these antennas is coupled by switch It: to the identifying system H at a particular moment, occur in timed relation to the initiation of a corresponding trace T of tube [2. Otherwise the trace pattern, which essentially comprises the superposition of a large number of similar trace patterns produced each second of operation, tends to drift across the screen of tube I2 and the deflections P and P or P" produced on the trace T are not readily indicative of distance of the radiated-signal reflector. Further, it is important that the wave-signal pulses of the identifying system it shall occur in timed relation to alternate half cycles of the alternating potential of source l9 since this source controls the alternate connection of the antenna systems l6 and I! to the identifying system It.

It is the purpose of the frequency divider I3- tov develop, from the high-periodicityrecurrentpulse modulation signal of-the locating system 10,; a lower-periodicity recurrent-pulse signal which may be applied to a modulation circuit of the identifying system Maud which has pulses bear ing a predetermined constant timev relationship to corresponding-pulses of the modulation signal of unit l0 and one pulse for each half cyclev of the alternating potential of source l9.

Referring now more particularly to theportion of the system embodying the present invention, the frequency divider I3 includes afirst p circuit comprising input-circuit terminals 2| adapted to have appliedthereto from the modulation-signalgenerator of unit It a high-perio dicity recurrrent-pulse signal which may have, for example, a periodicity of 800 pulses per second, but may in operation drift or change in an unstable manner over a small range of, say; 775

to 825 pulses per second. The frequency divider.

it also includes a second input'circuit comprising a resistor 22 adapted to have applied thereto a periodic control signal having a periodicity substantially lower than that of the signal applied to the input-circuit terminals 2| and nonintegral with respect thereto. For convenience, the signal applied to the input-circuit terminals 2| will hereafter be referred to simply as the input signal, While the signal applied to the inputcircuit resistor 22 will be called the controlsignal. In particulaiythe control signal is applied to the resistor 22 from the alternating-potential source l9 through a transformer 23 having a center-tapped secondary winding 24 connected in a full-Wave rectifier circuit which includes a pair of two-terminal rectifier devices 25 and 26 The frequency divider l3 also includes repeater means for combining the last-mentioned signals and responsive to the combined amplitudes thereof for repeating during each period of the control signal only a portion of the combined signals-including only a limited number of pulses of the input signal. In particular, the repeater means repeats only the portion of the combined signals which exceeds a predetermined amplitude level. The wave form of the control signal and this pre-- determined amplitude level are so chosen that only alimited number of pulses of the input signal are repeated with substantial amplitude during each period of the control signal. This means comprises a vacuum-tube repeater device 21 having a first'pair of input electrodes, comprising a control electrode 28 and a cathode 29, coupled to the input-circuit'terminals 2| of the divider I3 through a multivibrator 30 which is of conventional construction and may include two vacuumtube repeaters having the input circuit of each coupled to the output circuit of the other. This multivibrator is used as a frequency divider'for convenience in reducing by one-half the periodicity of the input signal. used between the input electrodes 28, 29 of the repeater 21 and the output circuit of the multivibrator 30 includes a series coupling condenser 3| and'a shunt resistor 32 which have circuit values'so selected as to perform a differentiation of the recurrent-pulse signal developed. in the output circuit of themultivibrator 36.

The vacuum-tube repeater 21 also includes a second pair of input electrodes, comprising the is provided for the repeater 21 so to bias the" latter that the signals electronically combined by this tube-' are repeated thereby only when the" The coupling circuit combined signals exceed a predetermined amplitude level which is suiliciently high that only a limited number of pulses of the input signal are repeated with substantial amplitude during each period of the control signal. This biasing means comprises a cathode resistor 35 included in the cathode circuit of tube 21 and a resistor 35 which couples the ungrounded terminal of the cathode resistor 35 to a source of unidirectional potential, indicated as +3. The unidirectional bias thus developed across the cathode resistor 35 is applied to the control electrode 28 of tube 21 through the resistor 32 and is applied to the screen electrode 33 of tube 21 through a grid resistor 31. The anode of tube 21 is energized from a unidirectional potential source, indicated as +B.

There is also provided pulse-responsive means responsive to at least one selected pulse of the pulses repeated by vacuum tube 21 and which occur during each period of the control signal for initiating a pulse of a recurrent-pulse signal and for thereafter rendering the pulse-responsive means unresponsive to any pulse repeated during the remaining portion of the period of translation of the signals combined by tube 21 following the one selected pulse. This means comprises a multivibrator 38 of conventional construction, similar to that of the multivibrator 38, having an input circuit coupled through a condenser 39 to the cathode resistor 35; The values of the circuit components of the multivibrator 38 are. so selected that, when the operation is controlled by input pulses thereto from tube 21, the recurrentpulse signal developed in the output circuit thereof is of constant average periodicity equal to that of the control signal and has a pulse duration slightly greater than the period of the input signal. To this end, the values of certain of the circuit components of the multivibrator 38 are so selected that the multivibrator initiates a cycle of its operation upon the first of the repeated pulses of substantial amplitude applied to its input circuit and thereafter renders itself unresponsive to any repeated pulses during an immediately subsequent interval equal to a substantial portion of the period of the control signal.

The frequency divider l3 additionally includes a signal-translating channel coupled to the input-circuit terminals 2| and responsive to the recurrent-pulse signal developed in the output circuit of the multivibrator 38 for translating, during each pulse of the latter signal, the input signal to derive a recurrent-pulse signal having a predetermined time relationship with the input signal, but an average periodicity equal to that of the control signal. This means comprises a vacuum-tube repeater 40 having a first pair of electrodes including a control electrode 4| and a cathode 42 coupled through a condenser 43 to the input-circuit terminals 2| and a second pair of input electrodes including the cathode 42 and a screen electrode 44 coupled through a condenser 45 and a grid-leak resistor 46 to the output circuit of the multivibrator 38. A grid-leak resistor 41 is provided for the control electrode 4| of tube 40. The anode of the tube 40 is energized through a resistor 48 from a source of unidirectional potential, indicated as +3, and is coupled through a condenser 49 to the modulation input circuit of the system 4 and through the univibrator 20 to the control circuit of the system H! and to the horizontal-scanning generator 9, as previously output circuit of the latter tube due to a nega- 8 of Fig. 2, the high-periodicity recurrent-pulse input signal applied to the input-circuit terminals 2| of the frequency divider I3 is represented by curve a of Fig. 2 and consecutive pulses thereof are numbered from to 8 for convenience in referring thereto. This signal is applied through the coupling condenser 43 to the control electrode 4| of vacuum tube 40,.but is not repeated to the tive-bias potential developed on the screen electrode 44 of this tube in a manner presently to be described. The input signal is also applied to the input circuit of the multivibrator and alternate pulses thereof, for example pulses I, 3, 5, 1, etc., initiate successive cycles of operation of the latter. The values of certain components of the multivibrator 30 are so selected, in a manner well known in the art, that the natural or free-running period of oscillation of the multivibrator is slightly longer than twice the period of the input signal. Further, certain of the circuit components have values so selected that the control electrode of the first tube of the multivibrator is positive for an interval slightly less than the period of the input signal, the controlelectrode potential of this tube having the wave form represented by curve b. The anode potential of this first tube of the multivibrator is represented by curve 0 and is applied as a recurrentpulse signal through the coupling condenser 3| to the repeater device 21.

As previously mentioned, the coupling condenser 3| and resistor 32 have values so selected that these circuit components diiierentiate the recurrent-pulse signal developed in the output circuit of the multivibrator 30, thus to develop and apply to the control electrode 28 of the tube 21 a symmetrical recurrent-pulse signal having a wave form represented by curve d. The vacuum tube 21 is so biased, however, by the potential developed across its cathode resistor 35 that the signal applied to its control electrode 28 is repeated by this tube only when its screen electrode 33 has applied thereto a potential positive with respect to its cathode 29.

As earlier mentioned, the potential applied to the screen electrode 33 of tube 21 is the control signal derived from thealternating current source 9 by the full-wave rectifier system comprising the transformer 23 and rectifier devices 25 and 26. This control signal is applied to the screen electrode 33 through the coupling condenser 34. As is well known, the latter establishes the electrical or equal-area axis of the control signal so that the potential as applied to the electrode 33 is as represented by curve e of Fig, 2 and may have a maximum positive value of approximately volts. During the interval t; to 252, Fig. 2, when the screen electrode 33 is positive, the positive pulses of the recurrent-pulse signal applied to the control electrode 28 of tube 21 are repeated by this tube and are developed across the cathode resistor 35 thereof. It may be noted that the negative pulses of the signal applied to the control electrode 28 are not repeated to the output circuit of tube 21 since the unidirectional bias developed across the cathode resistor 35 and applied through the resistor 32 to the control electrode 28 is sufilciently large that tube 21 is biased to anode current cutofi in the absence of any signal on its control electrode 28 so that the negative pulses of the applied signal simply bias the tube 21 below anode current cutoiT. The recurrent-pulse signal thus repeated by the tube 21 and developed across its cathode resistor 35 is represented by curve I of Fig. 2. It is thus evident that the tube 2] effectively electronically combines the input and control signals and is responsive to their combined amplitudes for repeating during each period of the control signal only a portion of the combined signals including only a limited number of pulses of the input signal.

It will be apparent from the foregoing described operation that the pulses of this signal have a fixed time relationship wtih particular ones of the pulses of the input signal and have an average periodicity equal to that of the control signal. The signal repeated by tube 21 is applied through the coupling condenser 39 to the input circuit of the multivibrator 3 3. Each pulse of the repeated signal initiates a cycleof operation of the multivibrator and the values of the circuit components thereof are so selected, in a manner well known in the art, that the natural or free-running frequency of the multivibrator is at least slightly longer than the period of the control signal. Certain of the circuit components of the multivibrator 38 are so selected that the control electrode of the first tube thereof is driven to a positive potential for an interval slightly less than the period of the input signal, the potential applied to the control electrode of this tube thus being as represented by curve 9. The anode potential of the second tube of the multivibrator 38 varies in the manner represented by curve h of Fig. 2. and the alternating component of this potential is applied through the coupling condenser d5 to the screen electrode M of the vacuum-tube repeater 40. The screen electrode 46 becomes conductive during each pulse of the signal applied to the control electrode 4|, thus to charge the condenser :15 and develop across the resistor 66 a bias potential which biases the tube All to anode current cutofi' in the intervals between the pulses of the signal applied to the screen electrode. Consequently, the vacuum-tube repeater 50 repeats to its output circuit the recurrent-pulse signal applied to its input electrode M only during each pulse of the recurrent-pulse signal applied to its screen electrode 44. It will be recalled that the control electrode of the first tube of the multivibrator 30 becomes highly negative just prior to the occurrence of a pulse of the input signal next succeeding the pulse which initiated a cycle of operation of the latter, as shown by curve b. Hence, the differentiated positive pulse of the recurrent-pulse signal developed by the condenser 3| and resistor 32 and repeated by the vacuum tube 27 so controls each cycle of operation of the multivibrator 38 as to cause the initiation of each pulse of the recurrent-pulse signal developed in the output circuit of the latter unit at a moment slightly preceding the occurrence of a pulse, for example the pulse numbered 4 in curve a, of the input signal. This conditions the vacuum-tube repeater 40 to repeat such pulses of .the input signal to develop in the output circuit of this vacuum tube a recurrent-pulse signal of relatively low average periodicity equal to that of the control signal and having pulses thereof occurring synchronously with and of the same wave form as corresponding pulses of the input signal. The signal thus derived by the operation of tube 40 is represented by curve 2' of Fig. 2 and is applied through the coupling condenser ie to the units It and it to effect the operation heretofore described. I

While applicant does not intend to be limited to any particular circuit values in the embodiment of the invention described, there follows a 10 set of circuit values which are found to be particularly suitable for a frequency divider of the type shown in Fig. 1:

Resistor 22 ohms 235,000 Resistor 32 do 47,0001 Resistor 35 do 100,000 Resistor 36 megohms 2.21 Resistor 37 d0 1.0 Resistor 46 i do 3.3 Resistor 47 do 1.0 Resistor 48 ohms 22,000 Condenser 31 micromicrofarads 500 Condenser 34 microfarad 0.1 Condenser 39 micromicrofarads 3,000 Condenser 43 do 3,000 Condenser 45 microiaradu 0.01 Condenser 49 micromicrofarads 3,000 Rectifier devices 25 and 26 Type 5U4G Tube 27 Type GSJ! Tube 40 i Type 6SJ7 +3 vo1ts 295i Periodicity of signal at input terminals 21 pulses per second 725-825 Frequency of source 19 cycles per seconds 60 As previously mentioned, the multivibrator 30 is conveniently used'to reduce by one-half the periodicity of the signal applied to the input electrode 28 of tube 2'1, as compared with that of the input signal applied to the input-circuit terminals 25. It has the additional function of causing the pulses of the recurrent-pulse signal applied to the input electrode 44 of tube 40 to lead in point of time certain pulses of the input signal, thus to condition tube it) to translate all portions of each of these certain pulses. It will be apparent, however, that this multivibrator may, if desired, be replaced by a conventional univibrator or. that the frequency divider of the invention may even be somewhat simplified by omitting the multivibrator alto ether, since neither of the functions performed by the latter are essential to the operation of the invention. Further, the multivibrator 38 may likewise be replaced by a conventional univibrator. While unit 38 operates to generate a recurrent-pulse signal which controls the operation of the repeater tube 48, it will be apparent that the frequency divider of the invention may be further simplified by omitting the latter tube and by directly utilizing the recurrent-pulse signal generated by the multivibrator 38 as the signal which is applied to the units l0 and Id in the same manner and; for the same purpose as thesignal applied thereto from tube 40.

While the time scale for the curves of Fig. 2 is such that only two pulses are repeated by the vacuum tube 21 during each interval when its screen electrode 33 is positive, it will be apparent that the operation described will be the same even though a larger number of pulses are translated by tube 2'! during this interval. This is true for the reason that the multivibrator 38 initiates a cycle of its operation only on the first one of such translated pulses of substantial amplitude. It will be evident, however, that where a relatively large number of pulses are translated by tube 2'5? during the interval mentioned, various arrangements may be utilized in place of the multivibrator 38, or preceding the latter, whereby a selected translated pulse other than the first pulse of substantial amplitude may be'utilized to effect the cycle of operation which conditions the vacuum tube 40 to translate desired portions of the input signal. For example,

conventional countercircuits may be utilized to count pulses from the first one translated and to initiate a cycle of operation upon the occurrence of a subsequent selected translated pulse.

It will be apparent from the above description of the invention that a frequency divider embodying theinvention is adapted to provide a relatively high ratio of frequency division, and one in which the pulses of a derived recurrentpulse signal have a predetermined time relation to corresponding pulses of an input recurrentpulse signaL-yet an average periodicity which is not integral with that of the latter.

While there has been described what is at present considered to be the preferred embodiment of this invention, it will be obvious to those skilled in the art that various changes and modifications may be made therein without departing from the invention, and it is, therefore, aimed in the appended claims to cover all such changes and modifications as fall within the true spirit and scope of the invention.

What is claimed is: g

1. A frequency divider, comprising, a first input circuit adapted to have applied thereto a highperiodicity recurrent-pulse signal, a second input circuit adapted to have applied thereto a periodic control signal having a periodicity substantially lower than that of said first-mentioned signal and nonintegral with respect thereto, repeater means for combining said signals and responsive to the combined amplitudes thereof for repeating during each period of said control signal only a portion of said combined signals including only a limited number of pulses of said first-mentioned signal, pulse-responsive means responsive to at leastone selected pulse of said repeated pulses occurring during each period of said control signal for initiating a pulse of a recurrent-pulse signal and for thereafter rendering said pulse-responsive means unresponsive to any pulse repeated during the remaining portion of the period of translation of said combined signals following said one selected pulse, and a signal-translating channel coupled to said first input circuit and responsive to said last-mentioned recurrent-pulse signal for translating during each pulse thereof said first-mentioned signal to derive a recurrentpulse signal having a predetermined time relationship with said first-mentioned signal but an average periodicity equal to that of said control signal.

2. A frequency divider comprising, a first input circuit adapted to have applied thereto a highperiodicity recurrent-pulse signal, a second input circuit adapted to have applied thereto a periodic control signal having a periodicity substantially lower than that of said first-mentioned signal and nonintegral with respect thereto, repeater means for combining said signals and responsive to the combined amplitudes thereof for repeating during each period of said control signal only a portion of said combined signals including only a limited number of pulses of said first-mentioned signal, pulse-responsive means responsive to at least one selected pulse of said repeated pulses occurring during each period of said control signal for generating a periodic-pulse signal having an average periodicity equal to that of said control signal and-a pulse duration shorter than the-period of said first-mentioned signal, and a signal-translating channel coupled to said first input circuit and responsive to said generated pesignal to derive a recurrent-pulse signal having a predetermined time relationship with said firstmentioned signal and an average periodicity equal to that of said control signal. Y

3. A frequency, divider comprising, a first input circuit adapted to have applied thereto a. highperiodicity recurrent-pulse signal, a second input circuit adapted to have applied thereto a periodic control signal having a periodicity substantiallylower than that of said first-mentioned signal and nonintegral with respect thereto, repeater means for combining said signal and responsive to the combined amplitudes thereoffor repeating during each period of said control signal only a portion of said combined signals including only a limited number of pulses of said first-mentioned signal, pulse-responsive means responsive to at least one selected pulse of said repeated pulses occurring during each period of said control signal forinitiating a pulse of a recurrentpulse signal and for thereafter rendering said pulse-responsive means unresponsive to any pulse repeated during the remaining portion of the period of translation of said combined signals following said one selected pulse, a vacuum-tube repeater having input electrodes coupled to said first input circuit and to said last-mentioned means to have applied thereto said last-mentioned recurrent-pulse signal, and means for so biasing said vacuum-tube repeater that said firstmentioned signal is repeated only during each pulse of said last-mentioned recurrent-pulse signal to derive a recurrent-pulse signal having a predetermined time relationship with said firstmentioned signal but an average periodicity equal to that of said control signal.

4. A frequency divider comprising, a first input circuit adapted to have applied thereto a high periodicity recurrent-pulse signal, a second input circuit adapted to have applied thereto a periodic control signal having a periodicity substantially lower than that of said first-mentioned signal and nonintegral with respect thereto, repeater means for combining said signals and responsive to the combined amplitudes thereof for repeating during each period of said control signal only a portion of said combined signals including only a limited number of pulses of said first-mentioned signal, pulse-responsive means responsive to at least one selected pulse of said repeated pulses occurring during each period of said control signal for deriving a recurrent-pulse signal having an average periodicity equal to that of said control signal and a pulse duration less than the interval between the pulses of said high-periodicity signal, and a signal-translating channel coupled to said first input circuit and responsive to said last-mentioned recurrent-pulse signal for translating during each pulse thereof said first-mentioned signa1 to derive a recurrent-pulse signal having a predetermined time relationship with said first-mentioned signal but an average periodicity equal to that of said control signal.

5. A frequency divider comprising, a first input circuit adapted to have applied thereto a highperiodicity recurrent-pulse signal, a second input circuit adapted to have applied thereto a periodic control signal having a periodicity substantially lower than that of said first-mentioned signal and nonintegral with respect thereto, repeater means for combining said signals and responsive to the combined amplitudes thereof for repeating during each period of said control signal only a portion of said combined signals including only a limited number of pulses of said first-mentioned sig- 13 113.1, pulse-responsive means responsive to at least one selected pulse of said repeated pulses occurring during each period of said control signal for deriving a recurrent-pulse signal having an average periodicity equal to that of said control signal but with each pulse of said derived signal advanced in point of time with relation to that corresponding pulse of said first-mentioned signal which it is desired to translate, and a signaltranslating channel coupled to said first input circuit and responsive to said last-mentioned recurrent-pulse signal for translating with fidelity of wave form during each pulse thereof a pulse of said first-mentioned signal to derive a recurrent-pulse signal having a predetermined time relationship with said first-mentioned signal but an average periodicity equal to that of said control signal.

CHARLES J. HIRSCH.

14 REFERENCES orrn'n The following references are of record in the file of this patent:

5 UNITED STATES PATENTS Number Name Date 2,105,870 Vance Jan. 18, 1930 2,183,966 Lewis Dec. 19, 1939 m 2,221,666 Wilson Nov. 12, 1940 2,235,131 Wheeler Mar. 18, 1941 2,255,403 Wheeler Sept. 9, 1941 2,422,204 Meacham a June 1'7, 194'? FOREIGN PATENTS 15 Number Country Date Great Britain Aug. 8, 1939 

